Senolytics And Senotherapeutics In Neurodegeneration is an important component in the neurobiology of neurodegenerative diseases. This page provides detailed information about its structure, function, and role in disease processes.
Cellular senescence — a state of stable cell-cycle arrest accompanied by a pro-inflammatory secretory phenotype — is increasingly recognized as a driver of [neurodegeneration]. Senescent cells accumulate in the aging brain and in the context of pathological protein aggregation, secreting cytokines, chemokines, and proteases that collectively constitute the senescence-associated secretory phenotype (SASP).¹ The SASP triggers neuroinflammation, impairs microglial and astrocytic function, disrupts the blood-brain barrier, and creates a feed-forward cycle amplifying neuronal damage. Senolytics selectively eliminate senescent cells, while senomorphics suppress the SASP without killing the cells. Both approaches represent emerging therapeutic strategies for Alzheimer's disease, Parkinson's disease, ALS, and other neurodegenerative conditions.
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Multiple CNS cell populations undergo senescence during aging and neurodegeneration:
| Marker | Type | Significance |
|---|---|---|
| p16INK4a (CDKN2A) | CDK inhibitor | Gold-standard irreversible senescence marker |
| p21 (CDKN1A) | CDK inhibitor | p53-dependent early senescence |
| SA-β-galactosidase | Enzyme | Lysosomal marker active at pH 6.0 |
| γ-H2AX foci | DNA damage | Persistent DNA double-strand breaks |
| Lamin B1 loss | Nuclear envelope | Nuclear lamina degradation |
| SASP factors | Secretome | IL-6, IL-1β, TNF-α, MCP-1, MMP-3 |
Senolytics target the senescent cell anti-apoptotic pathways (SCAPs) — pro-survival networks involving BCL-2/BCL-XL, PI3K/AKT, and FOXO4-p53 that protect senescent cells from apoptosis.
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The first identified senolytic combination, developed by Zhu et al. in 2015.⁵ Dasatinib (an FDA-approved Src/tyrosine kinase inhibitor) targets senescent cell survival via Src kinase inhibition, while quercetin (a natural flavonoid) inhibits BCL-XL and other pro-survival pathways. Key evidence in neurodegeneration:
A BH3-mimetic that directly inhibits anti-apoptotic BCL-2, BCL-XL, and BCL-W proteins, activating intrinsic apoptosis in senescent cells. In brain-relevant studies, navitoclax eliminated senescent endothelial cells after irradiation, restoring BBB integrity and improving hippocampal-dependent memory. Key limitation: Limited BBB penetration and dose-limiting thrombocytopenia due to BCL-XL inhibition in platelets.
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A naturally occurring flavonoid identified as the most potent senolytic among 10 flavonoids screened by Yousefzadeh et al. (2018).⁷ Fisetin reduced p16INK4a expression and SASP markers in aged mice, extended lifespan, and improved cognitive performance in SAMP8 (senescence-accelerated) mice — a model of sporadic AD. In APPswe/PS1dE9 Alzheimer's disease mice, fisetin maintained synaptic markers and reduced CDK5 dysregulation.
Developed by Baar et al. (2017),⁸ this peptide disrupts the FOXO4-p53 interaction that protects senescent cells from apoptosis, selectively restoring p53's pro-apoptotic function. In aged mice, FOXO4-DRI improved physical performance and organ function. Clinical translation faces challenges in CNS delivery and peptide-based drug manufacturing.
Ouabain, digoxin, and digitoxin were independently identified as broad-spectrum senolytics in 2019.⁹¹⁰ They inhibit the Na⁺/K⁺-ATPase pump and sensitize senescent cells to apoptosis through upregulation of the pro-apoptotic BCL-2 family member NOXA. The narrow therapeutic window limits clinical applicability.
Senomorphics suppress the toxic SASP without killing senescent cells, potentially offering a safer CNS approach where cell replacement is limited.
mTOR inhibition by rapamycin dampens SASP production by blocking translation of IL-1α (an upstream SASP driver) and promoting autophagy. In AD mouse models, rapamycin reverses protein aggregation, promotes clearance of amyloid-beta, phospho-tau, and alpha-synuclein, and improves cognition.
An AMPK activator that acts as a senomorphic by activating the AMPK-mTOR pathway and inhibiting [cGAS-STING-mediated inflammatory signaling. In a Parkinson's disease mouse model, metformin ameliorated mitochondrial dysfunction and delayed astrocyte senescence via the Mfn2-cGAS pathway. The TAME (Targeting Aging with Metformin) trial is assessing general geroprotective effects.
The JAK-STAT pathway is a major SASP driver. Ruxolitinib significantly decreased IL-6, MCP-1, and GM-CSF secretion from senescent cells and improved physical function in aged mice.¹¹ In traumatic brain injury models, ruxolitinib inhibited ferroptosis and reduced neurodegeneration.
AD has the strongest evidence base for senescence-driven pathology. Tau-bearing neurons display senescence-associated transcriptomic signatures,⁴ and p16INK4a-positive senescent astrocytes and microglia accumulate in regions of tau pathology. Genetic and pharmacological clearance of senescent cells in tau mice reduces tangles, preserves neurons and synapses, restores cerebral blood flow, and improves cognition.² Gaikwad et al. (2024) demonstrated that senescence, brain inflammation, and oligomeric tau synergistically drive cognitive decline.
alpha-synuclein preformed fibrils induce cellular senescence with activation of p53 and [DNA damage] responses. The toxic interaction between alpha-synuclein and iron induces senescence (p16 and p21 upregulation) preceding nigral [dopaminergic] neuron loss. Postmortem substantia nigra tissue from PD patients shows elevated p21 expression.
TDP-43, the hallmark pathological protein in >95% of ALS and ~50% of FTD, drives cellular senescence when mislocalized. ALS-affected motor neurons display DNA damage, activated DDR, metabolic dysregulation, mitochondrial dysfunction, and elevated ROS — features consistent with senescence.
The first clinical trial of senolytics in neurodegeneration. The Phase 1 open-label pilot (NCT04063124) enrolled 5 adults with early-stage symptomatic [AD] for 12 weeks of intermittent oral D+Q. Results showed dasatinib was detected in CSF in 4/5 participants (CSF:plasma ratio 0.42–0.92%), confirming CNS penetrance. Quercetin was not detected in CSF. The treatment was safe with no serious adverse events.¹² A Phase 2 randomized controlled trial (NCT04685590) is underway.
A 12-week open-label pilot in 12 older adults with slow gait and MCI. Treatment: 100 mg dasatinib + 1250 mg quercetin for 2 days every 2 weeks. Results (2025): No serious adverse events; Montreal Cognitive Assessment scores increased significantly by 2.0 points in those with lowest baseline cognition.¹³
A Phase 1/2 open-label pilot (NCT04785300) at Mayo Clinic testing intermittent D+Q in 20 participants with MCI or [AD] and tau-PET biomarker positivity. Results pending.
Amor et al. (2020) pioneered CAR-T cells targeting uPAR (urokinase-type plasminogen activator receptor), a surface protein broadly upregulated during senescence.¹⁵ Anti-uPAR CAR-T cells efficiently ablated senescent cells in vivo, extending survival in cancer models and restoring tissue homeostasis in liver fibrosis. In 2024, prophylactic anti-uPAR CAR-T administration showed long-lasting efficacy against age-related metabolic dysfunction. CNS application requires solving CAR-T trafficking across the BBB.
Galactose-modified prodrugs exploit elevated SA-β-galactosidase activity in senescent cells, unmasking active senolytic agents only inside target cells. Combining this approach with PROTAC technology has yielded galacto-modified PROTACs (Gal-ARV-771, Gal-MS99) with enhanced selectivity and senolytic indices.
The study of Senolytics And Senotherapeutics In Neurodegeneration has evolved significantly over the past decades. Research in this area has revealed important insights into the underlying mechanisms of neurodegeneration and continues to drive therapeutic development.
Historical context and key discoveries in this field have shaped our current understanding and will continue to guide future research directions.